The above-reference patents relate to a technique referred to as partial multiple encryption or selective multiple encryption (interchangeably). This technique can be used to combine normally incompatible encryption techniques into a single television cable system or the like in order to render normally incompatible receivers operable on a common network. These documents relate to Sony Electronics' Passage™ selective multiple encryption technology.
Currently, the main way to get Digital Rights Management (DRM) encrypted content is through Internet connected Personal Computers (PCs). Another way is to translate some of the basic rights from CA-to-DRM (Conditional Access to Digital Rights Management) as is done with the OpenCable Uni-directonal Receiver (OCUR) board used to get Cable content to PCs encrypted using MS WMDRM (Microsoft Windows Media DRM). The OCUR board acts as a host for CableCARD™ (a trademark for a CableLabs compliant Point of Deployment module). After tuning and demodulation by the OCUR board, the scrambled content is sent to an inserted CableCARD. The CableCARD CA descrambles the content. Before returning to the OCUR board, the content is re-protected using DFAST (Dynamic Feedback Arrangement Scrambling Technique) copy protection. The OCUR board descrambles the copy protected content, and then re-scrambles it with DRM. As of this writing, MS WMDRM is the only approved and active DRM system in use with the OCUR board. The DRM encrypted content is formatted into IP packets and sent to the PC motherboard over the USB interface. The DFAST copy protection interface only handles Copy Control Information (CCI) containing 2 bits of data and defining only: Copy Once, Copy Never, and Copy Free. It is therefore difficult for a service provider to define business rules such as a rental period for downloaded content, e.g. content viewable for 1 or 2 days.